This study assessed the effect of hormone replacement therapy using estrogens and/or progestogens on the number of vessels in the proximal and distal urethra, vesicourethral junction and bladder of castrated adult female rats. Forty-five virgin adult rats (Rattus norvegicus albinus) castrated for at least 30 days were used. They were assigned to five groups; group I (control) received no medication; the others received via the subcutaneous route, respectively, 17-beta-estradiol (group II), medroxyprogesterone acetate (group III), a maize oil and benzyl acid solution - placebo (group IV) and 17-beta-estradiol combined with medroxyprogesterone acetate (group V), for a minimum of 28 days. Increased vascularization throughout the urinary tract, except in the distal urethra, was found following estrogen replacement alone. in the group that received combined estrogens and progestogens, no increase was found. It was concluded that estrogen replacement in castrated rats significantly increased the number of vessels in the lower urinary tract.